1. Field of the Invention
This invention relates to heart valves, and more particularly relates to replacement of diseased or injured heart valves.
2. Description of the Related Art
There are four valves in the heart that serve to direct blood flow through the two sides of the heart. On the left (systemic) side of the heart are: (1) the mitral valve, located between the left atrium and the left ventricle, and (2) the aortic valve, located between the left ventricle and the aorta. These two valves direct oxygenated blood from the lungs through the left side of the heart and into the aorta for distribution to the body. On the right (pulmonary) side of the heart are: (1) the tricuspid valve, located between the right atrium and the right ventricle, and (2) the pulmonary valve, located between the right ventricle and the pulmonary artery. These two valves direct de-oxygenated blood from the body through the right side of the heart and into the pulmonary artery for distribution to the lungs, where the blood becomes re-oxygenated in order to begin the circuit anew.
All four of these heart valves are passive structures in that they do not themselves expend any energy and do not perform any active contractile function. They consist of moveable xe2x80x9cleafletsxe2x80x9d that open and close in response to differential pressures on either side of the valve. The mitral and tricuspid valves are referred to as xe2x80x9catrioventricular valvesxe2x80x9d because they are situated between an atrium and ventricle on each side of the heart. The mitral valve has two leaflets and the tricuspid valve has three. The aortic and pulmonary valves are referred to as xe2x80x9csemilunar valvesxe2x80x9d because of the unique appearance of their leaflets, which are shaped somewhat like a half-moon and are more aptly termed xe2x80x9ccuspsxe2x80x9d. The aortic and pulmonary valves each have three cusps.
Heart valves may exhibit abnormal anatomy and function as a result of congenital or acquired valve disease. Congenital valve abnormalities may be well-tolerated for many years only to develop a life-threatening problem in an elderly patient, or may be so severe that emergency surgery is required within the first few hours of life. Acquired valve disease may result from causes such as rheumatic fever, degenerative disorders of the valve tissue, bacterial or fungal infections, and trauma.
Since heart valves are passive structures that simply open and close in response to differential pressures on either side of the particular valve, the problems that can develop with valves can be classified into two categories: (1) stenosis, in which a valve does not open properly, and (2) insufficiency (also called regurgitation), in which a valve does not close properly. Stenosis and insufficiency may occur concomitantly in the same valve or in different valves. Both of these abnormalities increase the workload placed on the heart. The severity of this increased stress on the heart and the patient, and the heart""s ability to adapt to it, determine whether the abnormal valve will have to be surgically replaced (or, in some cases, repaired).
Valve repair and valve replacement surgery is described and illustrated in numerous books and articles, and a number of options, including artificial mechanical valves and artificial tissue valves, are currently available. However, the currently-available options cannot duplicate the advantages of native (natural) heart valves. Some of the available mechanical valves tend to be very durable, but are problematic in that they are thrombogenic and exhibit relatively poor hemodynamic properties. Some of the available artificial tissue valves may have relatively low thrombogenicity, but lack durability. Additionally, even these artificial tissue valves often do not exhibit hemodynamic properties that approach the advantageous hemodynamic performance of a native valve. Some artificial tissue valves attempt to copy the form of native heart valves; such valves still fall short in durability and in hemodynamic performance.
James L. Cox, M.D. observed that during the natural embryological development, the human heart begins as a simple tubular structure, and changes its form during development based on its physiological function. Dr. Cox developed a tubular artificial heart valve, basing his research and development on the principle that xe2x80x9cform follows function.xe2x80x9d This principle can be restated for heart valves as: xe2x80x9cif an artificial valve can be created that truly functions like a native valve, its resultant form will be very similar to that of the native valve.xe2x80x9d The prosthetic heart valve that Dr. Cox developed based on this principle is discussed and disclosed in U.S. Pat. Nos. 5,480,424, 5,713,950 and 6,092,529. Each of these patents is hereby incorporated by reference in its entirety.
Dr. Cox""s work has resulted in promising heart valve technology that can lead to the development of a prosthetic heart valve that can approach the overall performance of a native heart valve. Such a valve would be durable, nonthrombogenic, and would exhibit advantageous hemodynamics performance.
Accordingly, there is a need in the art for an improved prosthetic heart valve having advantageous hemodynamic performance, nonthrombogenicity, and durability.
In accordance with one aspect of the present invention, a stentless prosthetic heart valve includes a plurality of thin, flexible leaflets, each having an inner face, an outer face, an in-flow edge, an out-flow edge and side edges. The plurality of leaflets are sewn together along at a least a portion of their side edges so as to form a substantially tubular valve structure having an in-flow end and an out-flow end. The adjacent leaflets are arranged so that their side edges are substantially aligned and the inner faces of the leaflets engage each other adjacent the side edges. The valve structure is movable between a closed position in which the out-flow edges of adjacent leaflets engage each other, and an open position in which the out-flow edges of adjacent leaflets are separated from each other except along the side edges so that the sewn portions of the side edges of the leaflets bias the leaflets toward a partially closed position.
In accordance with another aspect of the present invention, a stentless semilunar heart valve includes three thin, flexible leaflets, each having an inner face, an outer face, an in-flow edge, an out-flow edge, side edges and tab portions extending outwardly beyond the side edges and positioned adjacent the out-flow edge such that the leaflets are attached to each other along their side edges so as to form a substantially tubular valve structure having an in-flow end and an out-flow end. The tab portions of adjacent leaflets engage each other to form commissural attachment tabs and at least a portion of each commissural attachment tab is adjacent to the outer face of the adjacent leaflets.
In accordance with yet another aspect of the present invention, a stentless heart valve has a first leaflet having a leaflet main body, the main body having an inner face, an outer face, a proximal end, a distal end, a first side edge, and a first tab portion adjacent the distal end and extending from the first side edge, the first tab portion connected to the first leaflet main body through a first neck portion; and a second leaflet having a leaflet main body having an inner face, an outer face, a proximal end, a distal end, a second side edge, and a second tab portion adjacent the distal end and extending from the second side edge, the second tab portion having a longitudinal slot and connected to the second leaflet main body through a second neck portion. The first side edge of the first leaflet and the second side edge of the second leaflet are substantially aligned with and attached to one another and the inner faces of the first leaflet and the second leaflet engage each other adjacent the aligned side edges. The second tab portion is folded so that the first and second neck portions extend through the longitudinal slot of the second tab portion. In addition, the neck portions of the leaflets are not stitched.
In accordance with a further aspect of the present invention, a method for making a stentless tubular prosthetic heart valve involves providing a section of substantially flat, flexible material, cutting a plurality of leaflets out of the flat material so that each of the leaflets has an inner face, an outer face, a proximal end, a distal end, side edges, and tab portions adjacent the distal end and extending from the side edges, aligning the side edges of adjacent leaflets together so that the inner faces of adjacent leaflets engage each other adjacent the side edges, and sewing aligned side edges together so as to form a substantially tubular valve structure having an in-flow end and an out-flow end. Additionally, the plurality of leaflets can be accomplished using a non-contact cutting apparatus, such as but not limited to a laser.
Another aspect of the present invention is a method for manufacturing a prosthetic heart valve involving providing a first valve leaflet and a second valve leaflet, the leaflets being formed separately from each other, placing a portion of an inward face of the first valve leaflet against a corresponding portion of an inward face of the second valve leaflet, and attaching the inward face portions to each other. The inward face portions of the leaflets are attached at the side edges of the leaflets.
Yet another aspect of the present invention involves a method of manufacturing a heart valve involves providing first and second valve leaflets each having an integral tab portion at an end thereof, and folding the tab portions relative to each other to provide a commissural tab, the commissural tab being attached to the leaflets along a commissural tab line such that free ends of the tabs extend outwardly from the line.
In accordance with another aspect of the present invention, a prosthetic valve includes a plurality of valve leaflets comprised of a flexible material, each leaflet having an inner surface and an outer surface, each leaflet attached to another leaflet along an attachment line, a portion of an inner surface face of one leaflet being in facing relationship with a portion of an inner surface of another leaflet at the attachment line, and a commissural tab at an end of each attachment line. The tab having free ends configured for attachment to a blood vessel.
In accordance with another aspect of the present invention, the leaflets of a prosthetic valve are comprised of equine pericardium. The pericardium is fixed, such as in a glutaraldehyde solution.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.